Atmospheric NH3 and NO2 concentration and nitrogen deposition in an agricultural catchment of Eastern China

To assess the atmospheric environmental impacts of anthropogenic reactive nitrogen in the fast-developing Eastern China region, we measured atmospheric concentrations of nitrogen dioxide (NO2) and ammonia (NH3) as well as the wet deposition of inorganic nitrogen (NO3− and NH4+) and dissolved organic nitrogen (DON) levels in a typical agricultural catchment in Jiangsu Province, China, from October 2007 to September 2008. The annual average gaseous concentrations of NO2 and NH3 were 42.2 μg m−3 and 4.5 μg m−3 (0 °C, 760 mm Hg), respectively, whereas those of NO3−, NH4+, and DON in the rainwater within the study catchment were 1.3, 1.3, and 0.5 mg N L−1, respectively. No clear difference in gaseous NO2 concentrations and nitrogen concentrations in collected rainwater was found between the crop field and residential sites, but the average NH3 concentration of 5.4 μg m−3 in residential sites was significantly higher than that in field sites (4.1 μg m−3). Total depositions were 40 kg N ha−1 yr−1 for crop field sites and 30 kg N ha−1 yr−1 for residential sites, in which dry depositions (NO2 and NH3) were 7.6 kg N ha−1 yr−1 for crop field sites and 1.9 kg N ha−1 yr−1 for residential sites. The DON in the rainwater accounted for 16% of the total wet nitrogen deposition. Oxidized N (NO3− in the precipitation and gaseous NO2) was the dominant form of nitrogen deposition in the studied region, indicating that reactive forms of nitrogen created from urban areas contribute greatly to N deposition in the rural area evaluated in this study.